1. Field of the Invention
This invention is directed to the measurement of the swath-width of an agricultural crop with acoustic measuring devices mounted on opposite ends of the header of a combine or harvesting machine.
2. Discussion of the Background
When a combine is used to harvest a growing crop, the driver will commonly have to watch the ends of the header on the front of the machine in order to steer the machine into the crops being harvested close to the center of the crop swath being worked. Other agricultural machines employ auto-steering mechanisms to control the steering of the machine which provide a way to steer into the center of the crop swath. In both cases the goal is to keep the header as full of crop as possible.
U.S. Pat. No. 4,835,691, issued May 30, 1989 to Abraham Rotem et al., entitled "Positioning System Particularly Useful for Position Agricultural Implements," shows the use of two opposite facing acoustic transceivers. The two transceivers, each consisting of an acoustic transmitter and receiver, are located on one side of the header of an agricultural machine so that as the machine is headed along the rows of the crop, each transmitter transmits signals toward a row on the outside of each transceiver. Returned echo signals from the crop rows are then received by the respective receivers which are used to measure the distance of the transceivers from each of the two adjacent rows.
While the two transceivers of the Rotem et al. patent provide signals that may be used to maintain a position with respect to two adjacent crop rows, they do not allow the swath width to be measured and, therefore, they provide no information on crop yield during harvesting. Furthermore, the Rotem et al. system requires that planting be done in rows and it is not suitable for both non-row crops, such as small grains, and row crops, such as corn.
The use of acoustic transducers is also shown for the control of a road grader which is disclosed in U.S. Pat. No. 5,327,345, issued Jul. 5, 1994 in the name of Nielsen et al. In the system of the Nielsen, et al. patent, acoustic transducers are used to measure the vertical and lateral distance from a reference point of a reference circuit in order to control the vertical and lateral position of a grading blade. In one embodiment of the Nielsen et al. system, one of the transducers transmits an acoustic wave that is reflected off of the surface and is detected by both of the transducers. In another embodiment a pair of transducers is positioned orthogonally to one another to measure the distance between each transducer and a respective orthogonal reference.